This invention relates to window coverings, and more particularly to the field of Venetian blinds having front and rear panels of sheer or translucent fabric between which are arrayed a series of relatively opaque fabric slats or vanes which can be tilted for light control by means of limited rotation of a wind-up roll to which the front and rear panels are connected. The invention includes an improved product, fabricating technique and apparatus for fabricating such blinds, which technique can also be applied to forming multi-layered composite sheets used in other types of products and for other purposes.
The most familiar type of Venetian blind window covering comprises a series of rigid slats or vanes suspended and controlled by a ladder cord system. The slats are typically wood, plastic or metal, and rest on the ladder cord rungs. The rungs are secured to front and rear vertical cords whose upper ends are secured to circumferentially spaced locations on a wheel. Limited rotation of the wheel, by means of a control wand or cords, causes relative motion between the front and rear cords, which in turn tilts the rungs and vanes. The entire array can be raised and lowered by additional cords which act to lift a bottom rail.
A modified type of Venetian blind is disclosed in U.S. Pat. No. 3,384,519 to Froget. There, the ladder cord system is replaced by front and rear cloth panels to which the vanes are heat welded. Preferably, the cloth panels and vanes are all made of thermoplastic yams, to facilitate bonding by heat welding. Partial rotation of an upper drum, to which the panels are connected, shifts the panels relative to each other, thereby causing the vanes to tilt for light control. Another similar product is disclosed in French Patent No. 1,521,488 to Demerson. Demerson prefers films to woven fabrics, and discloses adhesive bonding of the vanes to the facing panels.
Several more recent patents are directed to modifications of Froget""s basic idea, wherein the vanes are made of flexible fabric, adhesively bonded to the front and back panels. Additionally, the entire array can be retracted from the window opening by winding it onto an upper wind-up roller by means of cords which lift a bottom rail. Representative of these patents are U.S. Pat. Nos. 5,287,908, 5,313,999, 5,320,154, 5,394,922 and 5,456,304, all assigned to Hunter Douglas, Inc., and a patent to Ren Judkins patent, U.S. Pat. No. 5,339,882.
U.S. Pat. No. 5,664,613 (and subsequently assigned to a company owned by the assignee of the present application) describes another form of construction for a fabric Venetian blind. A continuous panel of relatively translucent material forms one facing of the blind. To that panel is bonded a series of parallel fabric strips at uniform intervals. Each strip comprises two adjacent portions of dissimilar material, one being relatively translucent and the other relatively opaque. The free edge of the opaque portion is bonded to the facing panel, while the free edge of the translucent portion is bonded to the adjacent strip at the junction line of that strip""s two portions. The assembled translucent portions of the constituent strips become the second facing panel of the completed blind. That is, the second facing panel, rather than being a single continuous panel of fabric, is a composite of several parallel strips, each having a height dimension approximately equal to the width (or depth) of the vanes.
U.S. Pat. No. 5,888,639, assigned to Newell Operating Co., discloses in FIGS. 15-19 a fabric Venetian blind having a structure very similar to that disclosed in FIGS. 3-6 of my parent application, Ser. No. 08/947,608, filed Oct. 9, 1997 (which Figures are also found in the present application). As in my parent application, the product is a laminated assembly of previously formed three-element strips. However, the relationship of the individual components of each three-element strip, and the method of preparing each such strip for subsequent assembly to adjacent strips, is substantially different. Furthermore, the method of assembly of the three-element strips to each other is substantially different, in that the strips are cut to a predetermined length, prior to their lamination to each other, which length corresponds to the desired width of the fabric Venetian blind. The method of assembly disclosed in my parent application and herein, wherein the three-element strip is helically wound upon itself in partially overlapping successive layers, represents a substantial improvement in the speed and economy of manufacture.
U.S. Pat. Nos. 5,490,553 and 5,603,369, assigned to Hunter Douglas, disclose in FIGS. 16-19 a vertical blind wherein each vertical blind vane is formed of the same strip of material as an adjoining portion of a facing panel on one side of the vanes. The single facing is a composite of narrow vertical strips. The vane portion of this strip is doubled back on itself. Another patent assigned to Hunter Douglas, U.S. Pat. No. 5,638,880, discloses in FIG. 26 a vertical blind wherein the facing on one side of the vanes comprises a series of vertical strips of material, each joined along one vertical edge to an adjacent strip, and at the other vertical edge to both the adjacent facing strip on that side and a discrete piece of substantially rigid, planar material forming the vane. The patent further discloses that both a front and a rear facing may be fabricated of such strips, and the strips and vanes can be oriented in either the vertical or horizontal directions.
U.S. Pat. No. 4,631,217, also assigned to Hunter Douglas, discloses in FIG. 2 a honeycomb or cellular type of window covering wherein a series of pleated, balsa generally Z-shaped strips, each formed of a single piece of fabric, are bonded together in a manner whereby each strip forms the front portion of one cell, the rear portion of an adjacent cell, and a dividing wall between the two cells. The dividing walls, however, are incapable of functioning as the vanes of a Venetian blind type of product, because they remain substantially perpendicular to the front and rear faces of the window covering throughout the full range of expansion and collapse of the cells.
Known processes for manufacturing these prior art fabric Venetian blinds are complex, slow and costly, and have contributed to a high price for these otherwise attractive products.
Accordingly, it is a principal object of the present invention to create additional alternative three-element or multi-element strip configurations and bonding procedures which also lend themselves to the use of the more economical helical winding technique disclosed in my above-mentioned parent application.
The presently contemplated application for the disclosed invention is the formation of fabric Venetian blinds, using a technique of helically winding an elongated strip of fabric. In one embodiment of the Venetian blind, a three-portion strip is initially formed from three side-by-side, longitudinal, bands or portions of approximately equal width and length. Each edge of the central portion is joined by ultrasonic welding to an edge of the adjacent outer portion. The outer portions are formed of sheer or relatively transparent material, and the central portion is relatively opaque.
As a result of the helical winding process, the central portion becomes the blind vane, while the two outer portions ultimately become segments of the front and rear composite facings of the blind. Successive windings are staggered and partially overlapped so that two of the three portions of the underlying winding are covered by the overlying winding. Two longitudinally extending glue lines are applied along the underside of the infeeding overlapping strip, these being positioned to bond together adjacent windings. A tube-like wound structure is formed which, when cut open along a line perpendicular to the helix angle, will result in a fabric Venetian blind. The disclosed method of fabrication thus differs significantly from the prior art. Indeed, this product and its benefits could not so economically be achieved by known manufacturing processes.
The strips, once assembled by the winding operation, produce both the flexible vanes and the front and rear face panels in a single continuous process. The resulting composite face panels comprise narrow, horizontal strips which have been joined successively to one another in the winding operation. The resulting flexible vanes swing between light-admitting and light-blocking positions upon relative movement between the two composite face panels.
Alternative constructions may include an additional layer of fabric in the vane portion, to create a pocket into which an opaque insert can subsequently be inserted, and the formation of products having multiple rows of vanes or central ligaments.
Another alternative construction relates to a modified three-element strip configuration wherein the entirety of one sheer strip more fully overlaps the relatively opaque vane strip, with one edge substantially aligned with a first edge of the vane and ultrasonically welded thereto, while the other sheer strip is slightly lapped under and ultrasonically welded to the second edge of the vane. The vane is slightly wider than each of the sheer strips, permitting the vane to be simultaneously welded to each of the sheers without interference by overlapping the other sheer at the desired weld zone.
The novel winding technique disclosed herein may also be used to fabricate products from other types of materials or intended for other fields of use. For example, multi-layered materials made from thermally non-conductive or reflective material may be made for insulation applications; polarized or tinted films may be used to create desired optical effects; and materials of selected porosity may be used to form air filtration products.
Also disclosed is the use of a resiliently deformable circumferential surface on a nip roll which functions to steer the sheet-like material which is driven by the roll set when differential pressure is applied to the two ends of the deformable roll.